1. Field of the Invention
This invention relates to a synchronizing pulse signal generation device for generating a pulse signal in synchronism with the horizontal and vertical synchronizing signal contained in a video signal.
2. Description of the Prior Art
Generally, a video signal contains a horizontal synchronizing signal (hereinafter will be called H-Sync signal) and a vertical synchronizing signal (hereinafter will be called V-Sync signal). Apparatuses handling such video signals, therefore, often utilize a pulse signal which is synchronized with these two kinds of synchronizing signals. Heretofore, a device for generating a pulse signal of this kind has been arranged to adjust the phase of the pulse signal to that of the video signal by resetting, with the H-Sync and V-Sync signals separated from the video signal, a frequency divider which forms pulses by frequency dividing clock pulses produced from a free-running oscillator.
However, the clock pulses produced by the oscillator of the pulse signal generating device are not always in synchronism with the video signal. Hence, the pulses may possibly be produced at a maximum time-base error corresponding to one clock pulse depending on the timing of the above-stated resetting operation. In order to minimize the time-base error, the oscillator must be arranged to oscillate at a very high frequency. This, however, necessitate the provision of an additional circuit element for high frequency at each applicable part of the apparatus. Further, the use of a high frequency signal brings about a serious adverse effect on peripheral circuits. Then, some suitable shielding arrangement becomes necessary for preventing such an adverse effect.